In recent technologies, a brushless motor having a rotor, which is embedded, therein, with plural permanent magnets, arranged in place at a predetermined distance relative to an inner periphery of a stator, of which a stator core is wound with coils, has been widely applied to an electric vehicle. A stator core is of cylindrical structure and is integrally formed with plural teeth protruding in a radially inner direction from an outer periphery thereof. These plural teeth are wound with coils. Portions of each coil, which appear axially outwardly from ends of the stator core, are, in general, referred to as coil ends. A rotor is formed in such a manner that a rotor core, which is attached, therein, with plural permanent magnets, is integrally equipped to a shaft, and is inserted into an inner side of the stator with the windings so as to be seated therein. The rotor rotates in response to electromagnetic force that is generated by electrically exciting the stator windings, as needed.
This type of conventional brushless motor is disclosed in JP2000-184645A and is described below with reference to FIG. 15. As is clearly illustrated in FIG. 15, a rotor 120 is equipped with a rotor core 121, permanent magnets 122, a pair of end plates 123, a shaft 124 and rivets 125. The rotor core 121 is a laminated body which is formed with plural core plates 126 that are layered. The rotor core 121 is held, at both axial ends thereof, by the pair of end plates 123, and is integrally fixed to the end plates 123 by means of the plural rivets 125. The core plates 126 each has a penetrating hole 126a, which is defined at a central portion of each core plate 126 and is employed for inserting the shaft 124 thereinto, plural penetrating holes 126b, which are defined at an outer peripheral side of the penetrating hole 126a and are employed for the plural rivets 125, and plural penetrating holes 126c, which are defined at a further outer peripheral side of the penetrating holes 126b and are employed for attaching the plural permanent magnets 122 thereinto. The respective permanent magnets 122 are inserted into the plural penetrating holes 126c and are fixed thereto. Each of the pair of end plates 123 has a penetrating hole 123a, which is defined at a central portion thereof and is employed for inserting the shaft 124 thereinto, and plural penetrating holes 123b, which are defined at an outer peripheral side of the penetrating hole 123a and are employed for the plural rivets 125. The respective rivets 125 are inserted into the plural penetrating holes 123b of the pair of end plates 123 and the plural penetrating holes 126b of the core plates 126. Both ends of the respective rivets 125, which appear axially outwardly from the end plates 123, are caulked.
In this type of conventional brushless motor, a running torque is generated by electrically exciting, in a vertically sectional direction of a rotational axis, a stator core 111, the rotor core 121 and the permanent magnets 122. That is, a magnetic field, which generates a running torque, is not effectively applied to spaces axially defined between coil ends 112a and the end plates 123. Therefore, in this type of conventional brushless motor, these spaces have not effectively contributed to generation of a running torque. As a result, an axial length of the motor is extended in response to a thickness (an axial length) of the coil ends 122a, or of the end plates 123. Moreover, the end plates 123 hold the permanent magnets 122 in an axial direction, the magnets 122 which have been housed in the rotor core 121.
The present invention has been made in view of the above circumstances, and provides a motor of which axial length can be abbreviated. Further, the present invention provides a motor which enables increasing in a degree of torque.